Positioning jig and positioning method for molding

Abstract

To provide a highly precise measurement reference for measurement.SOLUTION: A positioning jig for molding comprises a pair of frame bodies for sandwiching a blank and includes one or more markers each of which protrudes or is recessed from an upper surface of a first frame body. The marker has a pyramidal or frustum shape. A method for positioning a blank with the jig includes: sandwiching an edge of the blank between the pair; and measuring a shape of the blank with reference to the marker.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The following disclosure relates to a jig for subjecting a blank such as a metal sheet to incremental forming such as dieless forming, and a positioning method using the jig. [Background technology]

[0002] Classically, press forming using dies has been used to form metal sheets. Dies are generally expensive, and their production requires considerable manpower and effort, making press forming inconvenient for short-term production runs, for example. Dieless forming is a type of incremental forming, in which a thin sheet is fixed in the surface direction by a jig, and a tool is pressed perpendicularly against the surface while moving parallel to the surface, gradually forming the thin sheet. When combined with numerical control (NC), this method is usually referred to as dieless NC forming. Patent Document 1 discloses related technology.

[0003] Whether it is press forming or incremental forming, springback due to the inherent elasticity of metal sheets is unavoidable, which has a significant impact on dimensional accuracy. In dieless forming, the springback pattern is complex and difficult to predict due to repeated localized and non-uniform plastic deformation. To improve the accuracy of dieless forming, attempts are made to measure the difference from the target shape each time forming is performed and to modify the target shape to reflect the difference. This is called "anticipation" or "compensation." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2006-051547 Summary of the Invention [Problem to be solved by the invention]

[0005] As a prerequisite for conducting predictive analysis accurately and efficiently, it is necessary to measure the 3D shape of the blank (material) in the process of being formed with high accuracy. The problem is where to place the reference for shape measurement, but since the blank itself deforms each time it is formed, placing the reference on the blank will impair accuracy. The following disclosure relates to a positioning jig and positioning method that can provide a high-accuracy measurement reference. [Means for solving the problem]

[0006] The positioning jig for molding consists of a pair of frames that sandwich the blank, and the first frame has one or more markers that protrude or sink into the upper surface, the markers being cone-shaped or frustum-shaped. A method for positioning the blank using such a jig includes sandwiching the edge of the blank between the pair of frames and measuring the shape of the blank using the markers as a reference. [Effects of the Invention]

[0007] The fixture with markers replaces the blank itself and provides a precision reference for shape measurement. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view illustrating dieless forming. [Figure 2] FIG. 2 is a flow chart of the molding process including anticipation or compensation. [Figure 3] FIG. 3 is a schematic elevational view illustrating the prospecting or compensation process. [Figure 4] FIG. 4 is a plan view of the blank held in the jig. [Figure 5] FIG. 5 is a cross-sectional elevation view of the blank clamped in the jig. [Figure 6] FIG. 6 is a perspective view and a plan view of a marker according to a first example. [Figure 7] FIG. 7 is a perspective view and a plan view of a marker according to the second example. [Figure 8]FIG. 8 is a perspective view and a plan view of a marker according to a third example. [Figure 9] FIG. 9 is a perspective view and a plan view of a marker according to the fourth example. [Figure 10] FIG. 10 is a perspective view and a plan view of a marker according to the fifth example. [Figure 11] FIG. 11 is a perspective view and a plan view of a marker according to the sixth example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Several exemplary embodiments will be described below with reference to the accompanying drawings. It should be particularly noted that the drawings are not necessarily drawn to scale, and therefore the dimensional relationships between the drawings are not limited to those shown. Throughout the following description and the appended claims, and for the sake of convenience, a distinction is made between upside down, left side, front side, and back side, but embodiments in which the structure is optionally inverted, rotated, and reversed are possible.

[0010] The jig and method disclosed below can be suitably used for incremental forming, such as dieless forming, which combines three-dimensional shape measurement with numerical control (NC). Of course, the use of NC is not essential, shape measurement is not limited to three dimensions, and this embodiment does not necessarily require incremental forming. This embodiment may be used for press molding or three-dimensional additive manufacturing. The following description relates to the case of dieless forming as an example.

[0011] Referring to Figure 1, in incremental forming, a blank 1 made of a metal plate such as a steel plate is first clamped at its edge in a jig 3 and fixed to an NC processing machine. Referring further to Figures 2 and 3, a target shape P is set and input into the NC processing machine (step S1). Next, the NC processing machine presses a tool 5 against the blank 1 in the Z direction as indicated by arrow 7V, and drives it in the X and Y directions as indicated by arrow 7R according to the target shape P. The blank 1 gradually undergoes plastic deformation, thereby achieving dieless forming (step S3). Figure 1 depicts a round, pot-bottom-shaped dent 9 as an example of the formed result, but of course a variety of shapes can be formed.

[0012] Referring mainly to Figure 3(a), the blank 1, which had a flat initial shape S, assumes an intermediate shape 9a after a series of forming processes, but due to springback, there is still a difference from the target shape P. Therefore, the blank 1 in the process of being formed is temporarily removed from the NC processing machine together with the jig 3, and its shape is measured using an appropriate 3D shape measuring machine (step S5). The shape measurement may be any of point cloud measurement, line cloud measurement, and surface measurement, and the difference ΔP1 between the intermediate shape 9a and the target shape P at each point on the blank 1 is calculated based on the measurement.

[0013] The calculated difference ΔP1 can be compared with, for example, a predetermined threshold value. When the difference ΔP1 at each point on the blank 1 is equal to or less than the threshold value, it can be determined that the accuracy is sufficient (step S7). The blank 1 can be subjected to a subsequent process such as trimming (step S11) and become a product.

[0014] Generally, precision is insufficient in a single forming run, so a new shape is set by so-called estimation or compensation (step S9). That is, based on the difference ΔP1, a new estimated shape C1 is set by adding a compensation amount to the target shape P, as shown in Figure 3(b), and this is input into the NC processing machine. The estimated shape C1 may be determined by human judgment or may be calculated automatically from the difference ΔP1. In parallel, the blank 1 in the process of forming is fixed again to the NC processing machine. Based on the estimated shape C1, forming is performed again (step S3), followed by shape measurement (step S5).

[0015] If the difference ΔP2 of the intermediate shape 9b is still not equal to or less than the threshold value even after forming using the estimated shape C1, as shown in Fig. 3(c), a new estimated shape C2 based on the difference ΔP2 is set as shown in Fig. 3(d), and forming is repeated. Steps S3 to S9 are repeated until sufficient accuracy is achieved.

[0016] Needless to say, achieving sufficient accuracy and the efficiency of achieving it depend on the accuracy and efficiency of shape measurement. Therefore, how to set a reference for shape measurement is important. Even if a reference was set on the original blank 1, the blank 1 undergoes deformation during forming, making the original reference no longer useful. Furthermore, residual stress remains in the blank 1 during forming, so further deformation is likely to occur during the process of removing it from the jig 3 and then reattaching it. These factors significantly impair the accuracy of shape measurement. Even a slight change in the inclination of the blank 1 significantly changes the results of three-dimensional shape measurement, making it difficult to even perform measurement without a reference. Therefore, in this embodiment, shape measurement is performed using the jig 3 itself, which has a stable shape, as a reference. For this purpose, the jig 3 is equipped with one or more markers 11.

[0017] 4 and 5 in combination with FIG. 1, the jig 3 generally comprises a pair of first and second frame members 3A and 3B. The frame members 3A and 3B are each sized so that the edge of the blank 1 can be sandwiched between them to secure the blank. The inner peripheries of the frame members 3A and 3B are provided with openings 13A and 13B, respectively, for forming the blank 1. The openings 13A and 13B do not necessarily have to have the same shape and can be designed independently, for example, depending on the load applied to the blank 1. Depending on the forming requirements, a template may be interposed between the blank 1 and the second frame member 3B.

[0018] Jig 3 also has a plurality of first bolt holes 15A for fastening frames 3A and 3B together. Jig 3 also has a plurality of second bolt holes 15B for fastening frames 3A and 3B together with blank 1 to base 17 on the NC processing machine. Base 17 has threaded holes corresponding to second bolt holes 15B, but does not necessarily have a hole corresponding to first bolt hole 15A. By using bolt holes 15A and 15B appropriately, both frames 3A and 3B are free from base 17 when fastening blank 1 to jig 3. After fastening, blank 1 and jig 3 become a single unit and can be attached to and detached from base 17 as a single unit. Needless to say, blank 1 and jig 3 are subjected to shape measurement as a single unit, and are positioned and fixed to base 17 as a single unit.

[0019] Furthermore, the jig 3 preferably has one or more markers 11 on the upper surface of its first frame 3A. In shape measurement, if the entire blank 1 is used as a reference, as already mentioned, an error of, for example, several millimeters or more may occur due to deformation. However, in this embodiment, by using markers 11 with stable position and shape, the error can be reduced to 0.1 mm or less. Furthermore, instead of or in addition to the upper surface of frame 3A, markers 11 may be provided on the lower surface of frame 3A or 3B.

[0020] Each marker 11 may have a two-dimensional shape that is flat on the top surface, but preferably has a three-dimensional shape that protrudes or recesses from the top surface for ease of reference during shape measurement. Referring to FIG. 6 in combination with FIGS. 1, 4, and 5, the marker 11 is, for example, a rectangular concave surface recessed from the top surface of the frame 3A. Having the marker 11 rectangular is advantageous in that it provides references in both the X and Y directions. However, as will be described later, the shape can take various forms, such as a polygon with three or more sides or a circle.

[0021] In the case of a rectangular parallelepiped as shown in Figure 6, the bottom surface 21 is easy to refer to, but the side surface 19 is difficult to refer to. This is because, in general, it is difficult to accurately capture a vertically standing surface using optical means. Therefore, preferably, the marker 11 is a cone surrounded by side surfaces 19 that form an obtuse angle with the top surface of the frame 3A, as shown in Figure 7. Alternatively, it is preferably a frustum further comprising a bottom surface 21, as shown in Figure 8. The bottom surface 21 is convenient as an accurate reference in the Z direction.

[0022] Needless to say, the cone or frustum shape is not limited to being recessed from the top surface, and the marker 11 may protrude from the top surface as illustrated in Fig. 9. In such an example, the top surface 23 can be referenced for the Z direction.

[0023] As mentioned above, the marker 11 is not limited to a rectangle but can be any polygon with three or more sides, and Fig. 10 shows an example of a hexagonal pyramid. By increasing the number of referenceable sides 19, it is possible to expect improved accuracy.

[0024] Alternatively, as shown in Figure 11, it may be circular. The lack of flat sides makes it inconvenient for alignment in the XY directions, but it is convenient for producing the marker 11, as it can be produced using a rotary tool. Alternatively, although there is no illustrated example, the side surface 19 may be partially flat and partially curved, and the bottom surface 21 and top surface 23 may similarly include flat and curved surfaces.

[0025] The number of markers 11 and their positions on the jig 3 can be appropriately selected in consideration of the effect on the accuracy and efficiency of shape measurement. For example, only one marker 11 may be used, but from the viewpoint of immediately identifying the orientation and tilt of the removed blank 1, it is advantageous to have multiple markers, preferably three or more. Furthermore, from the viewpoint of improving the efficiency and positional accuracy of tilt detection, it is better to place the markers away from the center, and if the jig 3 is rectangular as in the illustrated example, preferably near each vertex. Needless to say, the shape of the jig 3 can be any polygon with more than four corners.

[0026] The positional relationship of marker 11 with respect to the bolt holes can affect accuracy. That is, since no bolts are fastened near second bolt hole 15B, at least during shape measurement, there is no deformation due to the pressing force, and high accuracy can be expected. On the other hand, pressing force acts near first bolt hole 15A even during shape measurement, so deformation may occur and affect accuracy. Therefore, it is advantageous to position marker 11 away from first bolt hole 15A; that is, marker 11 is preferably positioned farther from first bolt hole 15A than from second bolt hole 15B.

[0027] Using the jig 3 equipped with such markers 11, the shape measurement and positioning of the blank 1 can be performed as follows: First, the edge of the blank 1 is sandwiched between the pair of frames 3A and 3B of the jig 3, and the first frame 3A is fastened to the second frame 3B using the first bolt hole 15A. Next, the shape of the blank 1 is measured using the markers 11 as a reference. Next, using the markers 11 as a reference, the frames 3A and 3B together with the blank 1 are fastened together to the base 17 using the second bolt hole 15B.

[0028] Since shape measurement and positioning can be performed using markers with high accuracy and stable positioning as references instead of a deformable blank, the incremental forming according to this embodiment can pursue precision and efficiency.

[0029] Although several embodiments have been described, modifications or variations of the embodiments can be made based on the above disclosure. [Industrial Applicability]

[0030] An incremental forming fixture is provided that includes fiducials for shape measurement. [Explanation of symbols]

[0031] 1 blank 3 Jig 3A First frame 3B Second frame 5 Tools 9 Dent 9a,9b intermediate shape 11 Marker 13A,13B opening 15A First Bolt Hole 15B Second bolt hole 17 Base 19 Side 21 Bottom 23 Top surface S initial shape P target shape C1, C2 prospective shape

Claims

1. A jig for positioning a blank, fixing it to a base, and forming it, a pair of first and second frames sized to sandwich and secure an edge of the blank between the pair; a plurality of first bolt holes for fastening the first frame body to the second frame body; a plurality of second bolt holes for fastening the first and second frames together to the base; One or more markers each having a cone or frustum shape surrounded by sides that form an obtuse angle with respect to the top surface of the first frame body, and protruding or recessed from the top surface; A jig equipped with:

2. The jig of claim 1 , wherein the markers each have a polygonal pyramid shape or a polygonal truncated pyramid shape.

3. The jig of claim 1 , wherein the markers are positioned farther from the first bolt holes than from the second bolt holes.

4. 2. The jig according to claim 1, wherein the first and second frames each form a polygon having at least four sides surrounding the molding opening, and the markers are disposed near three or more vertices of the polygon.

5. 1. A method of positioning a blank for forming, comprising: sandwiching the edge of the blank between the pair of jigs of claim 1; fastening the first frame body to the second frame body using the first bolt holes; measuring the shape of the blank using the marker as a reference; fastening the first and second frames together with the blank to the base using the second bolt holes; The method includes:

6. Setting an expected shape based on the measured shape; forming the blank based on the anticipated shape; 6. The method of claim 5, further comprising:

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